Moveable magnetic devices for electronic graphic displays

ABSTRACT

The invention includes moveable magnetic devices, for use in conjunction with electronic displays associated with computers and electronic devices enable manual input devices and control devices to be joined to the display, whereby the electronic device may be controlled, inputs may be made thereto, and the electronic display may be altered in correspondence to these inputs. In one aspect, the invention includes a fader controller comprised of a longitudinally extending track having a portion thereof extending over an image area of an electronic display, and a fader cap joined to the track for longitudinal sliding translation therealong. A plurality of permanent magnets are spaced along the track, and the fader cap includes at least one electromagnet. Conductive rails extend longitudinally on the track, and the fader cap includes contacts that electrically engage the conductive rails. Some of the fader cap contacts are connected to the electromagnet(s), and at least one track interacts with one contact on the fader cap to detect the instantaneous position of the fader cap. The electromagnets are actuated to translate the fader cap distally or proximally along the track. In another aspect, the invention provides a magnetic arrangement for joining one or more controller device to a flat panel electronic display, whereby controllers such as switches, knobs, and faders (slide controllers) may be superposed on the display.

REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of application Ser. No.09/670,610, filed Sep. 26, 2000, for which priority is claimed.

BACKGROUND OF THE INVENTION

This invention relates to computer input devices and, more particularly,to mechanical controller devices that may be combined with computergraphic displays and/or touch screen input devices.

Touch screen devices have become a commonplace user interface forelectronic devices, computers, and the like. Touch screens are typicallycombined with a display screen which is in close proximity to the touchscreen or which projects images through the touch screen. Under softwarecontrol, the display may present images, video, alphanumericinformation, and various combinations thereof. Moreover, the display maydefine corresponding areas of the touch screen as control input areas,through the presentation of control command words, iconic or graphicrepresentations of controls, or the like. Thereafter, an operator touchat an appropriate portion of the touch screen causes the software tocorrelate the touch position with the control command defined by thedisplay at that position, and to act on that command.

It is well known in the prior art to employ controller devices inconjunction with touch screen devices and computer displays to emulatethe sensation and feel of mechanical input devices, such as knobs,joysticks, and sliding (fader) controls. Such touch screen controllerdevices are described, for example, in the following U.S. patents issuedto the present inventors:

U.S. Pat. No. 5,572,239,

U.S. Pat. No. 5,977,955,

U.S. Pat. No. 5,805,146,

U.S. Pat. No. 5,805,145,

U.S. Pat. No. 5,936,613,

U.S. Pat. No. 5,774,115.

There are various arrangements known in the prior art to removablysecure such controller devices to a touch screen, computer display, or asuperstrate placed over either of these devices. One object of thepresent invention is to use magnetic assemblies to adhere controllerdevices to flat panel displays, with or without the combined use oftouch screen devices. A further object of the invention is the use of alinear magnetic drive in a fader controller to translate the fader capunder machine control, whereby automatic fader controllers may beapplied to flat panel displays, touch screens, and computer displays ingeneral.

SUMMARY OF THE INVENTION

The present invention generally comprises moveable magnetic devices foruse in conjunction with electronic displays associated with computersand electronic devices. In particular, the invention enables manualinput devices and control devices to be joined to an electronic display,whereby the computer or electronic device may be controlled, inputs maybe made thereto, and the electronic display may be altered incorrespondence to these inputs.

In one aspect, the invention includes a fader controller comprised of alongitudinally extending track having at least a portion thereofextending over an image area of an electronic display. A fader cap isjoined to the track for longitudinal sliding translation therealong, thevariable position of the fader cap corresponding to a selected inputvalue or to a control function. The cap may be moved manually along thetrack to change the input value or control function. The display outputmay be altered by the computer or electronic appliance in response tothe input/control function to comprise an interactive graphical userinterface.

A salient feature of the fader controller is a mechanism for driving thefader cap to any position along the track. The mechanism includes aplurality of permanent magnets spaced along the track and arranged withopposite poles in close proximity. The fader cap is provided with atleast one electromagnet having poles that are longitudinally opposed. Aplurality of conductive rails extend longitudinally on the track, andthe fader cap includes contacts that electrically engage the conductiverails. Some of the fader cap contacts are connected to theelectromagnet(s), and at least one track interacts with one contact onthe fader cap to detect the instantaneous position of the fader cap.

The power rails are selectively driven with a voltage that alternates inaccordance with the fader cap position, so that the electromagnet polesinteract with the permanent track magnets to translate the fader capdistally or proximally along the track. The fader cap thus may be drivenautomatically to any desired position along the track, whereby thecomputer or electronic appliance may place the fader cap any presetposition. The conductive rail associated with position sensing mayinclude a distributed resistance therealong, whereby changes in voltageon the position sensing rail may be correlated with the linear positionof the fader cap.

In a further embodiment of the fader controller, the number ofconductive rails may be reduced to two, comprised of a DC/common railand a resistive, position sensing rail. The fader cap includes a touchsensor circuit and a processor to drive alternately each of twoelectromagnets in the cap, and one of the rails includes a distributedresistance that enables the system to determine the instantaneousposition of the fader cap.

In another aspect, the invention provides a magnetic arrangement forjoining one or more controller device to a flat panel electronicdisplay, whereby controllers such as switches, knobs, and faders (slidecontrollers) may be superposed on the display. The controllers may beconnected to the computer or electronic appliance that is associatedwith the display to enable input functions and control functions to becarried out. The flat panel display output may be altered by thecomputer or electronic appliance in response to the input/controlfunction to comprise an interactive graphical user interface.

The magnetic arrangement includes, in one aspect, a pair of tracksmounted adjacent to the rear surface of a flat panel display, the tracksdisposed at the side and end margins of the display. A pair of bars areslidably secured to the side tracks and end tracks, respectively, eachbar spanning the rear surface of the display, and a magnet orelectromagnet is secured at the intersection of the pair of bars. Thebars may be translated along their respective tracks to selectivelyposition the electromagnet at any location that corresponds to a desiredlocation on the front surface of the flat panel display. The controllerdevice includes a magnet (permanent or electromagnet) that is attractedto the rear electromagnet, whereby the controller is secured to the flatpanel display. The controller may comprise any of the controller devicesdisclosed in the prior art, such as the patent application referencedabove, or exemplified in the patents referenced above.

As a variant of this approach, a single pair of tracks may be providedat either the sides or end of the rear surface of the display, and a barmay be slidably secured to the pair of tracks. A magnet or electromagnetis slidably secured to the bar, and translation of the bar along thetrack combined with translation of the electromagnet along the barenable the positioning of the electromagnet at any selected locationcorresponding to a desired placement of a controller device on the frontsurface of the display. This arrangement may be compounded by theprovision of a plurality of slidable bars in adjacent relationship, eachsupporting at least one electromagnet to function as described above.

In a further aspect, the magnetic arrangement includes an extendable,rotatable arm secured adjacent to the rear surface of a flat paneldisplay. The arm includes a proximal end secured at one corner of thedisplay, and a distal end which supports an electromagnet or magnet. Asbefore, a controller device at the front surface of the display includesa magnet (permanent or electromagnet) that is attracted to the rearelectromagnet, whereby the controller is secured to the flat paneldisplay. The arm may be rotated and extended manually, or by motorsand/or linear actuators. As an alternative to the rotatable armarrangement, a multi-segment, hinged arm may be secured at the rearsurface and articulated by manual or motor means to position theelectromagnet to correspond to the desired placement of a controller onthe front surface of the display.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a side elevation of a fader controller having a linear drivefor moving the fader cap along the fader track.

FIG. 2 is an end elevation of the fader controller, taken along line 2—2of FIG. 1.

FIG. 3 is a functional block diagram depicting one arrangement ofmagnets for the linear drive fader controller of FIG. 1.

FIG. 4 is a functional block diagram depicting another arrangement ofmagnets for the linear drive fader controller of FIG. 1.

FIG. 5 is a graphic depiction of the electromagnet polarity timingrequired to translate the fader cap from left to right as depicted inFIGS. 1, 3, and 4.

FIG. 6 is a graphic depiction of the.electromagnet polarity timingrequired to translate the fader cap from right to left as depicted inFIGS. 1, 3, and 4.

FIG. 7 is a schematic layout of the conductive rails extending along thetrack of the linear drive fader controller of FIGS. 1-4.

FIGS. 8A and 8B are schematic views of the electronic circuit foroperating the linear drive mechanism of the embodiment of FIGS. 1-4.

FIG. 9 is a flow chart depicting the general operation of the fader capmicroprocessor of the circuit of FIG. 8.

FIG. 10 is a flow chart depicting the general operation of the mainmicroprocessor of the circuit of FIG. 8.

FIG. 11 is a cross-sectional side elevation depicting a furtherembodiment of the invention, in which a controller is secured to adisplay using a magnet behind the display.

FIG. 12 is a cross-sectional side elevation depicting another embodimentof the invention, in which a controller is secured to a display using amagnet behind the display.

FIG. 13 is a rear elevation of the present invention, showing oneembodiment for supporting moving magnets at the rear surface of adisplay.

FIG. 14 is a rear elevation of the present invention, showing anotherembodiment for supporting moving magnets at the rear surface of adisplay.

FIG. 15 is a rear elevation of the present invention, showing atelescoping pivoting arm for supporting a moving magnet at the rearsurface of a display.

FIG. 16 is a rear elevation of the present invention, showing anarticulated arm for supporting a moving magnet at the rear surface of adisplay.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention generally comprises moveable magnetic devices foruse in conjunction with electronic displays associated with computersand electronic devices. With regard to FIGS. 1 and 2, one moveablemagnetic device comprises a fader controller 21 that embodies thecapability to be automatically moved to a preset value or predeterminedposition. The fader controller 21 includes a track 22 extendinglongitudinally and having a base surface 23 that is adapted to besecured to an electronic graphic display, such as a flat panel display,VDT, or the like. The track is provided with a T-shaped cross section,with the base surface 23 comprising the lower surface of the stem of theT section. (A fader cap 24 is secured to the track 22 for free slidingtranslation Ad therealong. The fader cap 24 includes low frictionbearing surfaces that engage the upper, lower, and side surfaces of theupper portion of the T shape of the track to enable free translation.Other track cross-section configurations are possible, with concomitantmodifications of the fader cap to engage the track in freely slidingfashion. The cap 24 may be provided with a dished upper surface 26configured to accept a fingertip touch, so that the cap may be movedmanually along the track to any desired position.

Secured with the track 22 is a plurality of permanent magnets 27. Themagnets 27 are arrayed with their north/south polar axes in alignmentwith the longitudinal extent of the track, and with confronting ends ofthe magnets having opposite polarity. The magnets 27 are disposedclosely adjacent to the upper surface of the track 22, so that themagnetic fields intersect the fader cap to a maximum extent.

Disposed within the fader cap is at least one pair 31 of electromagnets,depicted with poles A and B spaced apart along a longitudinal axis. Theelectromagnet(s) is arranged to be selectively driven to reversepolarity, whereby the poles A and B of the electromagnet 31 willinteract with the permanent magnets 27 in the track 22 and generatelongitudinal force that drives the fader cap 24 to translate along thetrack. Alternatively, as shown in FIG. 4, a plurality of electromagnets31 may be disposed in the fader cap with a longitudinal spacing that issimilar to the spacing provided in the embodiment of FIG. 3.

The track further includes a plurality of conductive rails 32, as shownin FIG. 7, that extend longitudinally along the track 22. The rails maybe placed on any of the track surfaces that are engaged by the fadercap. The fader cap is provided with a plurality of brushes or contactsthat are disposed to extend to and electrically engage the conductiverails 32. In this embodiment, the rails 32 a and 32 b are connected,respectively, to A and B current supplies, rail 32 c is connected toCommon (ground), and rail 32 p is a Position rail, which may comprise adistributed resistance or other similar property for use in a subsystemfor determining the position of the fader cap 24 along the track 22.

With regard to FIG. 8A, the invention includes a driver circuit 33 foroperating the electromagnet 31 to translate the fader cap. The circuit33 includes a microprocessor 34 programmed appropriately to receiveinputs and produce outputs as described herein. The microprocessor isconnected to actuate driver 36, which is connected through rail 32 a toelectromagnet 37, and also connected to actuate driver 38 which isconnected through rail 32 b to electromagnet 39. Both electromagnets areconnected to common through rail 32 c. Either driver 36 or 38 is drivenalternately to switch the polarity of the magnets 37 and 39. It may beappreciated that the electromagnets may comprise a single unit that isdriven selectively to reversible polarity by the circuit 33. Inaddition, the position track 32 p is connected to common to form avariable resistance determined by the position of the fader cap alongthe track. The variable resistance is connected in parallel with a fixedresistance 41, the parallel combination being connected through an A/Dconverter 42 to the microprocessor 34, which correlates the digitalresistance signal from converter 42 with fader cap position, either byuse of a lookup table or a subroutine that calculates position fromresistance level. The circuit 33 may be embodied within the fader capitself, or may be disposed at the margin or periphery of a display of acomputer or electronic appliance to which the fader controller 21 isconnected. Alternatively, the circuit 33 may be embodied in the computersystem which controls such a display.

With regard to FIG. 5, there is shown the sequence for actuating thepolarity of electromagnets A and B in north, south, or off polarity totranslate the fader cap from right to left as depicted in FIGS. 1-4.Likewise the chart of FIG. 6 shows the sequence actuating the polarityof electromagnets A and B in north, south, or off polarity to translatethe fader cap from left to right. These sequences are also applicablefor the multiple electromagnet embodiment of FIG. 3. It may beappreciated that the computer or electronic appliance to which thecircuit of FIG. 8 is connected may selectively actuate the fader caplinear drive to translate the fader cap 24 to any desired position orpreset value along the track 22. Likewise, the graphic presentation onthe display associated with the fader controller 21 may be changed toindicate (numerically or graphically) the instantaneous position of thefader cap 24 and the position or value associated therewith.

With reference to FIG. 8B, the fader controller 21 may includes only twoconductive rails 32 r and 32 v, a reduction in number from the fourrails described previously. This embodiment may have particular utilityin fabricating small models of the invention, wherein the width of thetrack 22 is rather narrow. Conductive rail 32 r is connected to acurrent source 52, and includes a distributed resistance to serve as aposition indicator. Rail 32 v is connected to common or ground. Anonboard circuit 51 is mounted within the fader cap 22, and is connectedbetween the rails 32 r and 32 v to receive power therefrom. The circuitis arranged to move the fader cap to any selected position along thetrack, and to permit manual movement of the fader cap 22 to any desiredposition.

The circuit 51 includes a microprocessor 53 connected to a zenerregulated power supply 54 to receive a constant operating voltage. Atouch sensor circuit 56 is provided in the top surface of the fader cap24, and includes a signal line connected to an input of themicroprocessor 53 to conduct a touch signal thereto. Anothermicroprocessor input is formed by the output of voltage comparator 57,which has inputs connected across a resistor network that is spanned byswitch 58. A trio of single throw, double pole switches 61, 62, and 63are connected to electromagnet A, Common, and electromagnet B,respectively, and the switches are normally closed to ground. Eachswitch 61-63 has a normally open pole connected to current source 64,and an input triggers of switches 58 and 61-63 are connected torespective outputs of the microprocessor 53, whereby they areindividually, selectively actuated.

Whenever the touch sensor circuit 56 is activated by fingertip touch,and the touch is then removed, the circuit 56 signals the microprocessor53. The microprocessor 53 in turn actuates switch 58 for a short period;e.g., 1 msec. Switch 58 when closed shorts across its parallel resistor,and causes a momentary drop in the voltage on rail 32 r. This signalpulse appears at Vx, which is passed by normally closed contacts ofswitch 67 to A/D converter 68 and thence to main microprocessor 66,which in turn controls the electronic graphics display and associatedaudio control. Thus the computer or electronic appliance is signaledwhenever the fader cap 24 is touched.

It is noted that when the fader cap 24 is disposed in its most proximaldisposition, typically withdrawn to or beyond the margin of anelectronic graphic display, the resistance value of the distributedresistance in rail 32 r is substantially zero. The voltage Vx is thus amaximum, generally equal to the voltage across the zener diode connectedbetween supply and ground. When the fader cap 24 is disposed at its mostdistal position, typically extended into the image area of an electronicgraphic display, the value of the distributed resistance is maximum (onthe order of 10 ohms), and the voltage Vx drops to a known minimumlevel. Between these maximum and minimum levels, it is clear that thesteady state of voltage Vx is directly indicative of the position of thefader cap 24 along the track. Thus the main microprocessor 66 maydetermine the position of the fader cap at any instant.

The main microprocessor 66 may also send data and commands to the fadercap microprocessor 53. The microprocessor 66 may command the switch 67to close, connecting the normally open contact to single pole, doublethrow switch 71. Switch 71 is actuated by the microprocessor 66, withthe switch poles connected to differing plus voltage levels (such as 4vdc and 5 vdc). The switch 71 may be toggled selectively to generate apulse train of low-going pulses on the rail 32 r. These low-going pulsesappear across voltage comparator 57, which responds by generating a datapacket signal that is fed to the microprocessor 53. Thus the mainmicroprocessor may determine the fader cap position and receive touchsignals therefrom, and may also send data and commands to the fader cap.

With reference to FIG. 9, the functional flow chart for themicroprocessor 53 begins at Mode 1, and it first determines if there isa touch sense signal. If so, the microprocessor 53 deactivates switches61-63 to turn off the electromagnets A and B. At the end of touchsignal, the microprocessor sends an end of touch pulse to the mainmicroprocessor 66, as described above, and returns to Mode 1. If thereis no touch signal received, the system looks for a data packed receivedfrom the main microprocessor 66 (by a process described above). The datapacket may include such items as a new desired position, the number ofpulses that must be fed to the electromagnets to move to the newposition, the speed at which the cap is to move, and the direction thecap is to move. If there is a data packet, the system generates commandsto move the cap in accordance with the data packet. If no data packethas been received, the system returns to Mode 1 and begins a new loopexcursion.

With reference to FIG. 10, the functional flow chart for themicroprocessor 66 begins at Mode 1, and it first determines if there isan end of touch signal transmitted from the fader cap circuit, asdescribed above. If so, the microprocessor 66 reads the voltage Vx todetermine the cap position along the A track 22, and it changes theelectronic display graphics and audio control in accordance with the newcap position. If there is no end of touch pulse, the system looks for acap move request. If there is a cap move request, the system sends adata packet to microprocessor 53, which then carries out theinstructions as shown in FIG. 9. If there is no cap move request, theflow chart returns to Mode 1 and reiterates.

Thus manual positioning of the fader cap is recognized by the system asa command to change a control input and its associated graphicrepresentation on the electronic display. The system may also move thefader cap under machine control to a preset or predetermined positionand associated control input value. This latter function is very useful;e.g., in a situation in which a plurality of inputs are involved, and itis desirable to establish a previous arrangement of control levels.

There are other equivalent means and methods for carrying out some ofthe functions described with respect to the embodiments of FIGS. 1-10.For example, data packets may be exchanged between the fader cap circuit51 and the computer or electronic appliance by low power radio signal,optical signal., or the like. In addition, if the device used inconjunction with a touch screen device, the position of the fader capmay be determined by a touch signal generated by the fader cap circuitand/or provoked by a touch stylus extending from the fader cap.Furthermore, photovoltaic cells may be disposed in the fader cap toreceive light from the electronic display, whereby not only operatingpower for the fader cap circuit may be provided, but also positionsensing graphical data may be supplied to the fader cap. Likewise, thefader cap circuit may be provided with a battery power supply. Thusthere are various arrangements, including those shown in the U.S.patents referenced above and in the parent application referenced above,that may obviate the need for some or all of the conductive railsdescribed herein for powering the fader cap and transmitting positioninformation and movement commands. And, despite the seeming complexityof these embodiments described thus far, they may be produced as smallformat, crack-and-peel assemblies (described in the parent application)that are inexpensive and easily placed on or removed from an electronicdisplay, touch screen, superstrate, or the like.

In a further aspect of the invention, the track structure 22 on thedisplay, touch screen, or superstrate may be eliminated. With regard toFIGS. 11 and 12, a flat panel display 81 is provided with a cover glassor superstrate 82. Disposed below the display 81 is a structuralassembly 83 that supports a magnet 84. The magnet 84 may be permanent orelectromagnetic, and is mounted for sliding translation on the assembly83. Disposed at the outer surface of the superstrate 82 (or at the outersurface of the display 81, if no superstrate is provided) is a fader capcontroller 86 which includes a magnet 87 (permanent or electromagnetic)that engages the magnet 83 with sufficient force to retain the fader capcontroller 86 at the outer surface of the display/superstrate assembly.In the embodiment of FIG. 11, the fader cap controller is received in achannel-like groove in smoothly sliding fashion, whereby translation ofthe cap is guided in a linear direction. In the embodiment of FIG. 12,the fader cap 86 is slidably received on the surface of the superstrateor flat panel display, and is guided manually in accordance with agraphic presentation on the flat panel display. In either case, themagnet 84 is adapted to undergo translation in concert with the fadercap 86, so that adhesion to the display assembly is maintained. Thesliding surface of the cap 86 may comprise a polished material such asmetal or glass, a lubricious substance such as Teflon, or a cushioningmaterial such as felt or any other material that slides easily over thefront surface of the display assembly.

With regard to FIG. 13, one embodiment of the structural assembly 83includes a pair of rails 91 secured to the rear surface of a flat paneldisplay 92 and spaced apart to be outside the side margins of the imagearea 93 of the display 92. Another pair of rails 93 are secured to therear surface of the display 92 outside the end margins of the image area93. A bar 94 is slidably mounted on the rails 91, and another bar 96 isslidably mounted on the rails 95. At the intersection of the bars 94 and96 a magnet 97 (electromagnet or permanent magnet) is secured. The bars94 and 96 may be fabricated of transparent material, particularly forback-lighted displays. Translation of the bars 94 and 96 in rectilinearformat is carried out to position the magnet 97 at any desired locationbehind the display, corresponding to any desire location of amagnetically adhered controller device on the front surface of thedisplay assembly. In addition, the position of the magnet 97 may move inconcert with the movement of the controller at the front surface, undercontrol of the microprocessor that operates the display assembly andassociated computer or electronic appliance.

In a further embodiment of the invention, shown in FIG. 14, a pair ofrails 101 are secured to the rear surface of a flat panel display 102outside the end margins of the image area 103. At least one, andpreferably a plurality of bars 104 are slidably mounted on the rails101, spanning the image area 103 and each supporting a magnet 106(electromagnet or permanent magnet). Each magnet 106 is individuallytranslatable along its respective bar 104, whereby a plurality ofmagnets 106 may be arrayed behind the display to support a likeplurality of magnetically adhered controller devices throughout theimage area 103. Each bar 104 may be translated along the rails 101 undermachine control, and each magnet 106 may be translated under machinecontrol along its respective bar 104. Thus, for example, a plurality offader cap controllers (or knob controllers described in related patentsand applications) capable of magnetic adhesion may be placed orscattered on the front surface of the display 102, and adhered torespective magnets 106. Changes in positions of the fader capcontrollers are detected by the microprocessor that operates the displayand its associated computer or electronic appliance, and the positionsof magnets 106 may be changed in concert to maintain magnetic adhesion.Translation of bars and magnets may be carried out using linearactuators, motor drives for pulley or rack and pinion arrangements, orany other mechanisms known in the prior art for such purposes.

With regard to FIG. 15, a further embodiment of the invention includesan arm 107 mounted on the rear surface of a flat panel display 108, thearm mount enabling rotation of the arm within an angular range thatcircumscribes the image area 109 of the flat panel display. The arm istelescoping (extendable) and rotatable under machine control, as iscommonly found in the art of robotics and related fields. At the distalend of the arm 107 is a magnet 111 (electromagnet or permanent magnet)that is capable of securing a controller device capable of magneticadhesion to the front surface of the display assembly. The arm 107 maybe rotated and extended to place the magnet 111 at any desired positionin the image area 109 to secure a controller device thereat, and may bemoved in concert with the controller (in the case of a fader capcontroller) or may secure the controller device at a fixed location (asin the case of a knob controller).

A further variant of this concept, shown in FIG. 16, includes an armassembly 112 secured to the rear surface of the display 113 outside ofthe image area 114 thereof. The arm assembly includes at least twosegments 116 and 117 that are hinged at pivot 118. A magnet 119 issupported at the distal end of the arm assembly 112, and is adapted tomagnetically adhere a controller device to the front surface of thedisplay 113. The segments 116 and 117 may be articulated using pulleyand cable mechanisms, or direct drive motors at the pivot points, orother mechanisms known in the prior art. As before, the arm 112 may berotated and extended to place the magnet 119 at any desired position inthe image area 114 to secure a controller device thereat, and may bemoved in concert with the controller (in the case of a fader capcontroller) or may secure the controller device at a fixed location (asin the case of a knob controller).

With regard to the embodiments of FIGS. 11-16, it may be appreciatedthat the control device secured to the front surface includes a magneticmember that may comprise a mass of ferromagnetic material, a permanentmagnet, or an electromagnet, any of which may be configured or polarizedto optimize engagement with the magnetic device disposed at the rearsurface of the flat panel display.

The foregoing description of the preferred embodiment of the inventionhas been presented for purposes of illustration and description. It isnot intended to be exhaustive or to limit the invention to the preciseform disclosed, and many modifications and variations are possible inlight of the above teaching without deviating from the spirit and thescope of the invention. The embodiment described is selected to bestexplain the principles of the invention and its practical application tothereby enable others skilled in the art to best utilize the inventionin various embodiments and with various modifications as suited to theparticular purpose contemplated. It is intended that the scope of theinvention be defined by the claims appended hereto.

What is claimed is:
 1. A fader controller, including: a track extendinglongitudinally; a plurality of magnets secured in said track, saidmagnets arrayed along the longitudinal extent of said track; a fader capsecured to said track and adapted for slidable translation therealong;at least one electromagnet disposed in said fader cap and disposed tointeract magnetically with said plurality of magnets in said track;means for supplying power to said at least one electromagnet; and, meansfor selectively actuating and reversing polarity of said at least oneelectromagnet.
 2. The fader controller of claim 1, wherein said meansfor supplying power includes a plurality of conductive rails extendinglongitudinally on said track.
 3. The fader controller of claim 2,wherein said fader cap includes a plurality of sliding contacts, eachdisposed to electrically engage at least one of said plurality ofconductive rails.
 4. The fader controller of claim 3, further includingmeans for detecting the position of said fader cap on said track.
 5. Thefader controller of claim 4, wherein said means for detecting includes adistributed resistance in one of said plurality of conductive rails. 6.The fader controller of claim 5, wherein another one of said pluralityof conductive rails is connected to a common potential.
 7. The fadercontroller of claim 5, further including at least one pair ofelectromagnets in said fader cap.
 8. The fader controller of claim 7,wherein said plurality of conductive rails includes a pair of conductiverails having selectively switchable positive or negative polarity, saidpair of electromagnets each connected between a respective one of saidpair of switchable conductive rails and said common rail, whereby eachof said pair of electromagnets may be selectively operated inselectively reversed polarity.
 9. The fader controller of claim 7,wherein said means for supplying power includes a current sourceconnected to said distributed resistance in said one of said pluralityof conductive rails.
 10. The fader controller of claim 9, wherein saidmeans for selectively actuating and reversing polarity includes a firstmicroprocessor disposed in said fader cap.
 11. The fader controller ofclaim 10, further including a plurality of switches disposed in saidfader cap and controlled by said microprocessor, said plurality ofswitches connected to selectively actuate and reverse polarity of saidpair of electromagnets.
 12. The fader controller of claim 11, furtherincluding touch sensor means secured in said fader cap and disposed torespond to manual touch on said fader cap.
 13. The fader controller ofclaim 12, further including a second microprocessor disposed externallyto said fader cap and said track and connected to said conductive rails.14. The fader controller of claim 13, wherein said second microprocessoris connected to an electronic graphics display with which said fadercontroller is operatively associated.
 15. The fader controller of claim12, further including means for transmitting a touch sensor signal tosaid second microprocessor to indicate manual movement of said fadercap.
 16. The fader controller of claim 15, further including means fordetermining the position of said fader cap on said track.
 17. The fadercontroller of claim 16, wherein said means for determining positionincludes means for supplying a constant current through said oneconductive rail, whereby the voltage supplied to said fader cap variespredictably with the position of said fader cap along said oneconductive rail.
 18. The fader controller of claim 17, wherein saidmeans for determining position includes means for receiving a voltagereading from said one conductive rail and converting said voltagereading to a position coordinate.
 19. The fader controller of claim 18,wherein said means for determining position includes subroutinesexecuted by said second microprocessor.
 20. The fader controller ofclaim 13, wherein said second microprocessor includes means fortransmitting a command signal to said first microprocessor to translatesaid fader cap to a selected position on said track.
 21. The fadercontroller of claim 20, wherein said means for transmitting includesmeans for applying an electronic command signal to one of saidconductive rails.
 22. The fader controller of claim 1, further includingmeans for releasably securing said track to a flat panel display. 23.The fader controller of claim 22, further including magnetic meansdisposed at a rear surface of said flat panel display, said trackdisposed at an opposed, front surface of said flat panel display, andferromagnetic means disposed in said track for attracting said magneticmeans and magnetically adhering said track to said front surface.